I think the title ‘Our Lady of Grace’ is a popular, albeit incorrect, synonym for ‘Mediatrix of all graces’. The title of Mediatrix was used by Catholics for Mary long before it became a well known title, and Mary herself was known to use it when speaking to certain saints, encouraging them to ask for the intercession of the Mediatrix that they might obtain every grace from God. The title “Our Lady” is generally reserved for approved apparitions, and I think that’s why you’re asking about whether or not the title Our Lady of Grace is attached to an apparition. Nevertheless, here is what the Church teaches on Mary Mediatrix:
Christ the one Mediator: Position of the Saints and Especially of Mary
- And who could think or say that the confidence so strongly felt in the patronage and protection of the Blessed Virgin is excessive? Undoubtedly the name and attributes of the absolute Mediator belong to no other than to Christ, for being one person, and yet both man and God, He restored the human race to the favour of the Heavenly Father: One Mediator of God and men, the man Christ Jesus, who gave Himself a redemption for all (1 Tim. ii. 5, 6). And yet, as the Angelic Doctor teaches, there is no reason why certain others should not be called in a certain way mediators between God and man, that is to say, in so far as they co-operate by predisposing and ministering in the union of man with God (Summa, p. III, q. xxvi., articles 1, 2). Such are the angels and saints, the prophets and priests of both Testaments; but especially has the Blessed Virgin a claim to the glory of this title. For no single individual can even be imagined who has ever contributed or ever will contribute so much towards reconciling man with God. She offered to mankind, hastening to eternal ruin, a Saviour, at that moment when she received the announcement of the mystery of peace brought to this earth by the Angel, with that admirable act of consent in the name of the whole human race (Summa. p. III, q. xxx., art. 1). She it is from whom is born Jesus; she is therefore truly His mother, and for this reason a worthy and acceptable “Mediatrix to the Mediator.” As the various mysteries present themselves one after the other in the formula of the Rosary for the meditation and contemplation of men’s minds, they also elucidate what we owe to Mary for our reconciliation and salvation. No one can fail to be sweetly affected when considering her who appeared in the house of Elizabeth as the minister of the divine gifts, and who presented her Son to the Shepherds, to the kings, and to Simeon. Moreover, one must remember that the Blood of Christ shed for our sake and those members in which He offers to His Father the wounds He received, the price of our liberty, are no other than the flesh and blood of the virgin, since the flesh of Jesus is the flesh of Mary, and however much it was exalted in the glory of His resurrection, nevertheless the nature of His flesh derived from Mary remained and still remains the same (de Assumpt. B. V. M., c.v., among the Opera S. Aug).
- Pope Leo XIII, Fidentem Piumque Animum
The liturgy today meditates on the Word made man and repeats that he is born of the Virgin. It reflects on the circumcision of Jesus as a rite of admission to the community and contemplates God who, by means of Mary, gave his Only-Begotten Son to lead the “new people”. It recalls the name given to the Messiah and listens to it spoken with tender sweetness by his Mother. It invokes peace for the world, Christ’s peace, and does so through Mary, Mediatrix and Cooperator of Christ (cf. Lumen Gentium, nn. 60-61).
- Pope Benedict XVI, 40th World Day of Peace